An enterprise customer may enable users (e.g., employees of the enterprise customer) to access communication services using a Private Branch Exchange (PBX). For example, the PBX can be used to enable the enterprise customer to subscribe to a limited number of connections to a circuit switched network, e.g., the Public Switched Telephone Network (PSTN). The limited number of connections can then be shared among a large number of employees. The PBX may then serve as an aggregate endpoint device. For example, the sharing of the limited number of external lines may be facilitated using an aggregate endpoint device such as a PBX.
Prior to transitioning services from a traditional circuit switched network to an Internet Protocol (IP) Multimedia Subsystem (IMS) network, many enterprise customers require similar capability from the IMS network. However, unlike traditional circuit switched networks, IMS networks are initially designed for single user endpoint devices. When a session directed towards a destination address (e.g., a user that is behind a PBX) served by an aggregate endpoint device is received, the IMS network elements need to determine to which aggregate endpoint device the session is to be directed. For example, the Serving-Call Session Control Function (S-CSCF), Home Subscriber Server (HSS), Application Servers (ASs), etc. need to process the session request to determine the appropriate PBX. The processing and data storage requirements may then be costly for the network service provider.